Embodiments described in the present disclosure relate generally to the field of solar cells and conversion of light energy into electrical energy with photonic bandgap structures.
In the field of solar panel cells it is desired that solar light be absorbed efficiently by a material, and converted into charge carriers that may generate an electrical current (photocurrent). Solar cells use a photon absorption process where an incoming photon generates charge carriers such as an electron-hole pair in the material. The photo-generated electron-hole pair may be converted into a photocurrent by applying an electric field separating the charge carriers in conducting elements.
This is a desirable outcome of a photo-generated electron-hole pair in a solar cell. Alternatively, the photo-generated electron-hole pair may recombine, emitting a second photon at the same or slightly different wavelength. The second photon may then escape the structure. Also, the photon-generated electron-hole pair may be trapped in the material by impurities and other defects, without generating a photocurrent. Further, scattering events in impurities and other defects may deplete the energy of the photo-generated electron-hole pairs, so that these may recombine, generating excess heat and unable to produce a photocurrent.
Current solar panel cell applications rely on amorphous silicon or similar bulk structures in order to optimize the conversion of absorbed photons into a photocurrent. Amorphous structures facilitate the re-absorption of photons that are re-emitted within the structure, increasing the charge carrier generation. However, amorphous materials have the problem of inefficient coupling of the generated charge carriers into a photocurrent, through an electric field. Thus, prior art applications of solar cells use complicated structures involving highly doped semiconductor regions next to Schottky barrier metals. Furthermore, in order to increase the amount of generated charge carriers, some technologies choose to use thicker slabs of materials. This increases the probability of trapping charge carriers in material defects before being coupled to a current flow out of the structure, thereby reducing photocurrent generation efficiency.
Current solar panel technologies present problems such as wear out, damage, and stress introduced in the structure by heating. Damage and heating in a solar panel is produced by absorption of the high content of ultraviolet (UV) and infrared radiation (IR) from the sun. Also, solar panel technologies face the problem that the efficiency of the photocurrent generation is highly dependent on the angle of incidence of radiation.
The sun provides radiation at variable angular orientations throughout the day. Thus, current technologies need to devise complicated mechanisms and architectures to compensate for the change in efficiency throughout the day.
Therefore, there is a need for solar panel cells that have increased efficiency for photocurrent generation. It is desirable that UV and IR radiation either be reflected by the solar panel cells to avoid damage to the structure or absorbed in materials having the appropriate band gaps to convert the radiation in photocurrent. It is also desired that the efficiency of the current generation process be equally high for all possible incidence angles of the radiation upon the solar panel. Current solar panel technology uses tracking devices to overcome this issue.